authority

“United States version of the English text of the eighth edition (2006) of the International Bureau of Weights and Measures publication Le Système International d’ Unités (SI)” This publication is the definitive guide for the United States, but the ultimate authority is the original, French version. For the symbols for the prefixes, see page 29; those for the seven base units, page 23; and those for derived units, page 25. Symbols for non-SI units, some of which were formerly part of “the metric system”, such as the hectare, are given on pages 32, 34, 35, 37 and 38.